Modern integrated circuit (IC) processes for implementing high-end processors and other complex ICs usually accommodate input voltages in a very restricted voltage range. For example, one conventional maximum operating range from minus 500 mV to positive 1.3V is typical for many ICs. Such ICs may use a special circuit to sense a voltage that ranges between a volt and a few tens of volts. Without a circuit to compress the voltage range of such a large-signal input, the IC may suffer from irreparable harm.
Conventionally, this range compression may often be accomplished with a resistive voltage divider. For example, by using a 30:1 ratio, the range can be compressed by a factor of 1/30. FIG. 1 shows one conventional supply voltage sensor 100 using a resistive voltage divider 110. The signal at the middle node 112 of the divider 110 is sensed and digitized by the sensor/digitizer 130, which may include an analog to digital converter. An output of the sensor/digitizer 130 is digitally gained back up by digitally multiplying by 30 using the multiplier circuit 120.
However, several challenges make it difficult to successfully implement the supply voltage sensor 100. First, the supply voltage sensor 100 typically needs a very high impedance compared to that of the resistive divider 110, which is a significant challenge when the divider 110 itself needs to operate on very low power, which implies a high impedance for the divider. Second, the sensor/digitizer 130 needs good linearity from tens of milli-volts up to about a volt. Such circuits can be designed, but usually such circuits rely on precision resistors, high value resistors, precision capacitors, inductors, wellmatched transistors, low leakage transistors, or other analog circuit elements that are generally not available on a process targeting digital logic. Conventional processors found in many of today's computing systems are generally implemented on a digital logic process with an inferior set of analog devices.